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Understanding services · England & Wales

What “they have capacity” means

Services may say an adult can decide for themselves, even when the decision seems dangerous or difficult to understand.

What capacity meansCapacity is not a blanket judgement about a person. It is about whether they can make one particular decision at the time it needs to be made. Mental illness, unusual behaviour or an unwise choice does not by itself prove that someone lacks capacity.

This guide covers England and Wales. Scotland and Northern Ireland have different laws.

Where to get advice in Scotland or Northern Ireland

Scotland: the Mental Welfare Commission’s carer advice page covers rights and mental-health or incapacity questions. Its free advice line is 0800 389 6809. Monday to Friday, 9am to midday and 1pm to 4pm. Contact details. The carer advice page explains what it can advise on.

Northern Ireland: use the Department of Health’s Mental Capacity Act FAQs. The Act has been partly commenced, so ask the team which legal framework applies to the decision in question.

How capacity is assessed

  1. Capacity is decision-specific. Someone may be able to decide what to eat but not be able to make a more complex decision about treatment or money.
  2. It is time-specific. Capacity can change. A person may be able to make the same decision at a different time.
  3. The starting point is that the person has capacity. They must also be given practical help to understand and make the decision before they are treated as unable to do so.
  4. An unwise decision is not enough. The law does not allow capacity to be rejected only because other people disagree with the choice.
  5. A proper assessment is needed where capacity is in doubt. It looks at whether an impairment or disturbance of the mind or brain means the person cannot understand, retain, use or weigh the relevant information, or communicate the decision.[1]

What you can ask

Clarify the assessment“Which specific decision was their capacity assessed for, and when was it assessed?”
Ask how they were supported“What information were they given, and what support was used to help them understand, weigh and communicate the decision?”
When capacity may fluctuate“What they can understand and manage changes during the day. Please record what I've seen. Does their capacity to make this decision need to be assessed again when their condition changes?”
Who assesses capacity?

The person responsible for the decision will usually assess capacity. For a treatment decision, that may be the clinician proposing the treatment. More serious or disputed decisions may need a more formal assessment. Ask who made the assessment and whether it is recorded.

What happens if they lack capacity?

Under the Mental Capacity Act, a decision made for someone who cannot make that particular decision must be in their best interests. They should be involved as much as possible, and their wishes, feelings, beliefs and values considered. The decision-maker must consider whether the same purpose can be achieved with less restriction of their rights and freedom.[2]

Family, friends and carers should normally be consulted where practical and appropriate. This does not mean the family automatically makes the decision.

Tell the team about any advance decision to refuse treatment, health and welfare lasting power of attorney, or court-appointed deputy. Ask them to check whether the document or legal authority applies to this decision. A valid, applicable advance refusal cannot simply be set aside because others think treatment would be best. Separate rules can apply to treatment under the Mental Health Act: ask which law is being used.[3]

Mental Capacity Act and Mental Health Act are different

The Mental Capacity Act covers decisions made for someone who cannot make a particular decision. The Mental Health Act has separate powers concerning assessment, detention and treatment for mental disorder. Someone can have capacity for a decision and still be assessed under the Mental Health Act. Being detained under the Mental Health Act also does not automatically mean they lack capacity for every decision.

Rethink Mental Illness explains the difference.

If you disagree with the assessment

Ask for the concern to be recorded and for an explanation of the decision and evidence used. Ask whether it should be reviewed because the decision, timing or person's condition has changed. For an unresolved concern about NHS care, the services-say-no guide explains PALS and complaints.

Related guides

They will not accept helpWhen services say noSectioning and Mental Health Act assessments
Sources and how this guide was written

  1. How capacity is assessed

    Government guidance on the Mental Capacity Act and the NHS Mental Capacity Act guide.

    Back to the advice

  2. Best interests and less restrictive options

    NHS guidance on the Mental Capacity Act explains involvement, consultation and considering less restrictive ways to achieve the purpose of care.

    Back to the advice

  3. Advance decisions and decision-making authority

    Government Mental Capacity Act guidance, sections 10 and 14, covers advance decisions, attorneys and the separate Mental Health Act framework. See also NHS guidance on advance decisions and health and welfare powers of attorney.

    Back to the advice
About the sources

This guide explains the Mental Capacity Act in England and Wales, using legislation, GOV.UK, NHS and Rethink guidance. Scotland and Northern Ireland have different laws.

Last full source check: 27 August 2026

Later checks: Resource routes checked: 1 October 2026. Best-interests decisions, less restrictive options and existing decision-making authority checked: 8 October 2026.

Mental Welfare Commission advice-line contact details checked: 8 October 2026.

Independent information, not a medical or crisis service. This guidance has not been clinically reviewed. How we use sources.

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